Multicasting is a well known method of transmitting messages to selected groups of users across a network, such as the Internet. One simple example of multicasting entails transmitting an E-mail message to a plurality of users that each are on a mailing list. Video conferencing and teleconferencing also use multicasting principles and thus, often are referred to as “multiconferencing.”
Security in multicast broadcasts is often provided by encrypting the data and dispensing a unique cryptographic key to each of the group members. In a multicast environment, each time the membership of the group changes the data group key must be redistributed to maintain security. Redistribution occurs via a unicast session between a key distributor and each member of the group. If the membership changes often, a new unicast session must be established for each member of the group and a new data group key must be sent. This constant rekeying is an inefficient use of bandwidth.